so i have a 20 gallon tank freshwater tank with 6 pearl danios, 2 cory's, and a red tailed shark. Today i noticed that one of my pearls is swimming kinda on a slant, and when he swims fast he kinda turns horizontal. He seems fine and hes swimming like he normally does except for the fact that he is on a slant. i think he might have swim bladder disorder, but im not sure. What do you guys think? Any help is much appreciated!